linux-kernel - [PATCH] eventfd: move 'eventfd-count' printing out of spinlock

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Message-ID: <tencent_6E80209FC9C7F45EE61E3FB3E7952A226A07@qq.com>
Date:   Tue, 26 Sep 2023 22:05:00 +0800
From:   wenyang.linux@...mail.com
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>,
        Christian Brauner <brauner@...nel.org>
Cc:     Wen Yang <wenyang.linux@...mail.com>,
        Christoph Hellwig <hch@....de>, Dylan Yudaken <dylany@...com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Matthew Wilcox <willy@...radead.org>,
        Eric Biggers <ebiggers@...gle.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] eventfd: move 'eventfd-count' printing out of spinlock

From: Wen Yang <wenyang.linux@...mail.com>

It is better to print debug messages outside of the wqh.lock
spinlock where possible.

Signed-off-by: Wen Yang <wenyang.linux@...mail.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Christian Brauner <brauner@...nel.org>
Cc: Christoph Hellwig <hch@....de>
Cc: Dylan Yudaken <dylany@...com>
Cc: David Woodhouse <dwmw@...zon.co.uk>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Eric Biggers <ebiggers@...gle.com>
Cc: linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
 fs/eventfd.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/eventfd.c b/fs/eventfd.c
index 33a918f9566c..6c5fe0f40aa5 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -295,11 +295,13 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c
 static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
 {
 	struct eventfd_ctx *ctx = f->private_data;
+	unsigned long long count;
 
 	spin_lock_irq(&ctx->wqh.lock);
-	seq_printf(m, "eventfd-count: %16llx\n",
-		   (unsigned long long)ctx->count);
+	count = ctx->count;
 	spin_unlock_irq(&ctx->wqh.lock);
+
+	seq_printf(m, "eventfd-count: %16llx\n", count);
 	seq_printf(m, "eventfd-id: %d\n", ctx->id);
 	seq_printf(m, "eventfd-semaphore: %d\n",
 		   !!(ctx->flags & EFD_SEMAPHORE));
-- 
2.25.1